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Arsenic - Alarm Warning!

by Sylvia Mortoza

The World Health Organization (WHO) safe limit for arsenic in drinking water is 0.01 mg/l. In Bangladesh the maximum permissible limit is 0.05 mg/l. 48 out of the 64 districts of Bangladesh now show a level of contamination higher then the maximum permissable limit. Cases of arsenic poisoning are pouring in from all over the country.

The toxic effect of arsenic is dependent on its chemical form; route of entry; age; sex; dosage and duration of exposure. The major portion of the absorbed arsenic is excreted through the urine (about 50 per cent); a small portion through faeces; skin; hair; and nails; and is firmly bound to Keratin. Storage in metabolically dead tissues slowly eliminates it from the body but when the poison is ingested at a rate higher than the body's disposal system, the result is any form of the arsenic-related diseases. In other words, if ingested faster than it can be excreted, arsenic accumulates in the hair and fingernails.

In Bangladesh, each of the four recognized stages of arsenicosis, or chronic arsenic poisoning, have been reached. The first two stages are before the condition becomes irreversable so it is important to catch them early.

  1. Preclinical: the patient shows no symptoms, but arsenic can be detected in urine or body tissue samples.
  2. Clinical: Arsenic-poisoning may begin with the irritation of gastro-intestinal and upper respiratory tracts. Various effects can be seen on the skin. A general darkening of the skin (melanosis) is the most common symptom - often observed on the palms. Dark spots on the chest, back, limbs, or gums have also been reported. Oedema (swelling of hands and feet) is often seen. A more serious symptom is keratosis, or hardening of skin into nodules, often on palms and soles. This consists of an overgrowth of the Kasatin skin-structure with the development of numerous warts, ridges on the finger-nails and coarseness of the hair.

WHO estimates that a period of five to ten years exposure to arsenic is needed to reach this stage.

The only treatment is to find the source of poisoning and to stop people from drinking the contaminated water.

Once past this stage, complications set in as clinical symptoms become more pronounced and the internal organs are affected. Enlargement of liver, kidneys, and spleen have been reported. Some research indicates that conjunctivitis (pinkeye), bronchitis and diabetes may be linked at this stage, to arsenic exposure. Symptoms may also indicate an inflammation of the peripheral nerves and if the condition is allowed to persist, palsies may set in and the patient becomes apathetic. The final stage is malignancy - when tumours or cancers (carcinoma) affect the skin or other organs. At this time affected persons may develop gangrene or skin, lung, or bladder cancer.

The United States Environmental Protection Authority (USEPA) estimates that the risk of developing skin cancer from a lifetime of drinking contaminated water is 5 in 100,000 per mgm/L arsenic. The required exposure times are not well understood, and doubtless depend on concentration, but WHO estimates that carcinoma can develop after ten to twenty years of exposure. If exposure in Bangladesh began fifteen years ago it may still be too early to detect an increase in mortality from cancer.

Examination of the liver-tissue of arsenic patients has disclosed a severe deficiency in selenium which is able to prevent the effects of the arsenic. Selenium in the diet is therefore essential for combatting exposure but this can be found only in eggs, milk and a few other foodstuffs that are all beyond the purchasing capcity of the poor.

In the light of recent epidemiological evidence linking arsenic and cancers, WHO in 1993 decreased its recommended maximum value for arsenic in drinking water from 0.05 to 0.01 mg/l. The USEPA and EC are considering revising their limits, currently at 0.05 mg/l. All of the standards are based on total arsenic content, regardless of speciation.

Although various treatment methods have been adopted to remove the arsenic from drinking water under laboratory and field conditions, the major mode is by physical-chemical treatment methods. Various treatment methods include:

  • adsorption-co-precipitation using iron and aluminium salts
  • adsorption on activated alumina/activated carbon/activated bauxite
  • reverse osmosis
  • ion exchange
  • oxidation followed by filtration.

The United States Environmental Protection Agency (USEPA) have summarised coagulation with iron and aluminium salts and lime softening as the most effective treatment process for removing arsenic from water to meet the interim primary drinking water regulations standard of 0.05 mg/L [30].

In the case of Bangladesh, inorganic arsenic in huge quanities (in thousand of tons) has been released into the groundwater. Tests in West Bengal revealed that one single tube well released 150 kg of arsenic/ year. If no safe remedial measures are quickly forthcoming, the only option is to return immediately to the use of surface water for drinking, bathing and irrigation. But as water collected from the rivers; ponds; lakes; canals; haors; etc. is polluted and must be purified by boiling or by the use of chemicals like aluminium sulphate or ferrous salts, finding a technology that will be simple and easy for people to use at a cost low enough is imperative.

One such technology is solar radiation. This is a simple and effective method that can be applied to combat water-borne and water related diseases that are prevalent in Bangladesh. Dr. O. Odeyemi, a visiting UNU Fellow at the Brace Research Institute in Quebec, Canada has focused mainly on the design and adaptation of systems that can be used and maintained by the 1.4 billion inhabitants of rural areas of the world. The process is so simple and it could be the immediate answer to the incidence of preventable water-borne and water related diseases - and it is attractive because it is a virtually costless way to render contaminated water fit for human consumption.

The technique involves exposing transparent glass or plastic bottles of water obtained from nearby streams and other sources, for a period of 2 to 4 hours to full sunlight. It has been noticed that under these conditions, harmful pathogenic organisms that may be present in the water are killed, provided the initial degree of water contamination is not excessive. Recent reports from Canada say they have had great success with transparent plastic bags filled with water.

As researchers have successfully demonstrated that sunlight will destroy much of the faecal bacteria present in contaminated drinking water - but the process is especially effective if the water contains a sufficient amount of oxygen. An easy way to ensure this is to oxygenate the water before hand by mixing it with air.

As solar photo-disinfection can be carried out in the home by individuals, families or small communities without any need for a significant financial investment or external agency support - (the only requirement being a sufficient number of bottles or clear plastic bags to provide enough drinking water to meet each person's daily needs) - solar water treatment might be the answer to the problem of arsenic-contamination for a low- income community like ours where the cost of engineering solutions may prove prohibitive.

An alternative technology that may be cost-effective is Ultra-violet Disinfection which uses an ultraviolet (UV) light source enclosed in a transparent protective sleeve. This is mounted in such a manner that the water that passes through the flow chamber admit the UV rays and absorb them into the stream. These rays are able to destroy bacteria and inactivate many viruses. This kind of system disinfects the water without the need for adding chemicals and as a result, possesses some of the benefits of distillation. It neither creates new chemical complexes nor changes the taste or odor of the water - and - it does not remove any beneficial minerals that may be in the water. Ultraviolet light safely and reliably disables the DNA of bacteria and viruses in local water supplies, destroying their ability to reproduce and rendering them harmless. It consists of a germicidal ultraviolet (UV) lamp positioned above a shallow water pan. Water flows through the unit by gravity, staying in the disinfection chamber for 12 seconds to ensure adequate disinfection. However if the water is partially treated by the sediment process and carbon filter prior to passing through the UV flow chamber, it is more effective.

UV Waterworks is one such system worth considering as an answer to the problem of arsenic-contamination in Bangladesh. UV Waterworks has a maximum flow rate of 15 liters (4 gallons) per minute. The electronic components are based on standard, off- the-shelf, mature technologies. The basic unit (Model UVW2.3NC) consumes 40 watts of electricity and accommodates 120 and 220 V AC or 12 V DC. The cost to operate UV Waterworks is approximately four cents per tonne of water.

Since UV Waterworks relies on gravity for water flow, it can be used with any water source. The only electricity needed is for the UV lamp, which means that it can be powered by a car battery, a bicycle pump generator, grid electricity or solar, wind or hydro power. (Solar, wind and micro-hydro power packages are available through the manufacturer World Health Incorporated). One unit feeding into an enclosed water storage tank can easily provide sufficient water for one household for all water uses or for a village of up to 1,500 people if water is used primarily for drinking and cooking. (In fact, one unit feeding water into a 5,000-10,000-gallon storage tank can serve approximately 150 homes in the United States, the highest water-use country in the world.) The size of the water storage tank needed depends on the volume of water needed during peak use hours in any one household or among all water users connected to the tank.


You are visitor West Bengal India & Bangladesh Arsenic Crisis since 7 Jan 98.  Page last modified 24 Sep 2002 .  Comments/problems email acic@bicn.com.

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